Cross-wound open mesh coil



Aug. 6, 1968 R. E. WH|PPLE CROSS-WOUND OPEN MESH COIL 2 Sheets-Sheet 1Filed Nov. l, 1965 Aug- 6, 1968 R. E. WHIPPLE 3,396,356

CROSS-WOUND OPEN MESH COIL Filed Nov. 1, 1965 2 sheets-sheet 2 UnitedStates Patent O 3,396,356 CROSS-WOUND OPEN MESH COIL Richard E. Whipple,Rochester, N.H., assignor to General Electric Company, a corporation ofNew York Filed Nov. 1, 1965, Ser. No. 505,824 3 Claims. (Cl. 336-189)ABSTRACT OF THE DISCLOSURE A novel cross-wound, open mesh coil andmethod of winding such coil. The open mesh coil is cross-wound on ailanged arbor using a thin-wall, hollow needle which presses the wireagainst the flange with a slight overthrow to help position the wirebefore the next traverse of the wire across the arbor. The cross-overpoints within the coil are bonded together by an adhesive overcoat onthe wire, which is cured. An open mesh resin material is applied to theinner and outer surfaces of the coil and bonded thereto by curing. Aspecic machine for winding the coil is also disclosed.

This invention relates to high voltage coils and more particularly tocross-wound open mesh coils and to the method of making such coils.

As is well known to those skilled in the electrical art, electricalapparatus is becoming smalle-r and more compact while at the same timebeing subjected to greater amounts of electrical current and voltage.Also, greater .use is being made of encapsulated components in suchelectrical apparatus. By encapsulated it is generally understood Atomean to completely encase a component in v an insulating resinousmaterial, with such material completely filling, as far as possible, allvoids in' the structure of the component, As is well understood, voidsin an electrical component subjected to high voltage leads to thedevelopment of corona in such voids. The corona generally leads todeterioration of the insulation and subsequent breakdown of theelectrical component.

In electrical coil manufacture most coils are Wound on an arbor witheach layer of the coil wound directly over the preceding layer. Thecoils are Wound as tightly as possible and depend on the insulation ofthe wire to provide necessary insulation between the various wire turns.For high voltage coils, layer insulation is sometimes placed betweeneach layer of the coil to provide additional insulation between thelayers. These types of coils cannot be adequately encapsulated becausethe encapsulating resin cannot penetrate the interstices of the coil andthus is not able to ll all of the voids between the various turns andlayers within the coil. When encapsulated coils of this construction aresubjected to high impulse voltages there is a tendency for corona todevelop in these unfilled voids. As above noted, this corona willeventually lead to the breakdown of the coil. To overcome these problemsa precision wound coil using open mesh insulation between the variouslayers of the coil has been considered. However, it has been found thatsuch coils cannot be adequately encapsulated without leaving a number ofvoids within the coil structure.

Another type of coil that has been considered for encapsulation is thecross-wound coil. This coil is sometimes referred to as a universalwinding. Coils of this type are known in the prior art such, forexample, as Patent No. 1,342,209. The cross-wound or universal coil hasgenerally been used for inductance coils because of the lowerdistributed capacity of this type of winding. Many attempts to produce across-wound coil for high voltage application have been unsuccessful.When wire having adequate enamel insulation has been used in cross-woundcoils the turns tend to fall off during winding. These turns provide3,396,356 Patented Aug. 6, 1968 ICC displaced wires which result inexcessive stresses being placed on the insulation between such displacedwires and adjacent wires. When fabric covered wire is used to form suchcoil, the fabric tends to hold the coil turns in the desired position,but the fabric covering prevents the encapsulating material from fillingthe voids in the coil.

It has recently been discovered that a cross-wound coil can be made fromwire having adequate enamel insulation by use of winding means whichfirmly position the end turns of the coil against the flanges of anarbor on which the coil is wound. It has also been discovered that aftersuch cross-wound coils have been Wound the coils may be dimensionallyand physically stabilized by the use of inner and outer layers of epoxymaterial which may be cured to stabilize the coil prior to removal ofthe coil from the arbor. It has also been discovered that coating meansmay be provided over the enamel insulation which may be cured prior toremoval of the coil from the winding arbor to stabilize the cross-woundcoil.

Therefore it is one object of this invention to provide a novel,cross-wound, open mesh high voltage coil.

A further object of this invention is to provide a dimensionallystabilized cross-wound, open mesh coil which may be readily encapsulatedin an insulating resinous material.

A still further object of this invention is to provide a novel method ofwinding a cross-wound, open mesh high voltage coil.

In carrying out this invention in one form, an open mesh, cross-woundhigh voltage coil is wound on a flanged arbor by means of a cross feedmechanism which causes the wire of the coil to be firmly positionedagainst the flanges of the arbor prior to the reverse traverse of thewire feed mechanism. The coil wound according to this invention in oneform is an open mesh coil dimensionally and physically stabilized bymeans of a cured overcoat placed on the wire enamel. According toanother form of the invention the cross-wound open mesh coil isdimensionally and physically stabilized by a layer of compatibleinsulating mesh material bonded to the inner and outer surfaces of thecoil.

The invention which is sought to be protected will be particularlypointed out and distinctly claimed in the claims appended hereto.However, it is believed that this invention and the manner in which itsvarious objects and advantages are obtained will be better understood byreference to the following detailed description of various embodimentsthereof, particularly when considered in the light of the accompanyingdrawing, in which:

FIGURE l is a perspective view of a cross-wound open mesh coil accordingto one form of this invention;

FIGURE 2 is a plan view of one form of winding machine, with portions inphantom, which may be used to wind the coil of FIGURE l; and

FIGURE 3 is a schematic view of one method of mounting the windingneedle on the winding machine.

Reference will now be made to the drawing wherein like numerals are usedto indicate like parts throughout the various views thereof. Referencering first to FIG. 1 of the drawing, there is shown a cross-wound openmesh coil 10 which comprises a plurality of turns of wire 12. As isclear from FIG. l, the various turns of wire 12 are cross-wound over thewidth of the coil 10 forming the desired open mesh coil 10. As will beapparent from FIG. 1, the wire 12 is wound angularly across the width ofcoil 10, sharply turning at each edge ofcoil 10, as indicated at 14, andreturning angularly across to the opposite edge of coil 10. This, ofcourse, produces an open mesh winding. According to this invention theopen mesh coil 10 may be wound with greater than 50% open area withinthe coil, While providing a dimensionally and physically stabilized coilwhich may be readily encapsulated with an encapsulating resin which maylill all of the interstices of the coil structure.

In a preferred form of the invention a B stage epoxy glass meshinsulation 16 is placed on a winding arbor prior to winding of coil 10.After the coil is crosswound on the arbor a second layer of B stageepoxy glass insulation 18 is tightly wound about the outside uppersurface of coil 10. In FIG. 1 the outer layer of epoxy insulation isshown as pulled back to better show the winding of coil 10. However, itwill be understood that the epoxy insulation 18 will be tightly woundabout the outer surface of coil 10. After the coil is wound and the Bstage epoxy insulation is in place, the coil will be heated to cure theepoxy insulation. The cured epoxy insulation will dimensionally andphysically stabilize the coil 10 securing the inner turns and preventingthe coil from spreading.

In another form of the invention the coil 10 is wound with wire 12 inwhich the wire 12 is provided with a coating over the enamel insulation.The overcoat on the enamel insulation is used to lock the adjacent turnsof the wire together at their cross-over points. One type of overcoatthat provides the desired adhesion of adjacent wires is a polyvinylbutyral resin. After winding of coil 10 it is heated while in place onthe arbor. The heating first softens and then cures the overcoat. Thiscuring effectively locks the adjacent turns of wire 12 at theircross-over points. Obviously, other material could be used as theovercoat as long as it is compatible with the wire enamel used.

Of course it will be understood that both the epoxy glass insulation andthe overcoat material may be used together if desired. In coilsutilizing wire of very small diameter, the overcoat material isparticularly useful in providing additional insulation foi' the coil, aswell as providing a more stable coil.

Also shown in FIG. l is an electrostatic shield member 20, the shieldmember is made of expanded metal and used in the manner particularly setforth in application Ser. No. 505,911 filed Nov. 1, 1965, now abandoned,for Electrostatic Shield for Encapsulated Electrical Apparatus, in thename of the present inventor and assigned to the same assignee as thisinvention. When the electrostatic shield 20 is used it is placed on thewinding arbor prior to the inner epoxy mesh insulation .16. Obviously,when the epoxy mesh insulation 16 is cured the shield 20 is firmlybonded to coil 10 in the desired position. Of course, it will beapparent to those skilled in this art that a. second electrostaticshield could be placed over the outer epoxy resin insulation 18 andfirmly bonded to coil 10 if desired.

The preferred method of making the cross-wound open mesh coil of `thisinvention is best shown in FIG. 2 of the drawing. FIGURE 2 shows a coilwinding machine 22 provided with a cross feed mechanism comprising a cammember 24 and pusher arm or cam follower 26. Of course, it will beunderstood that cam 24 will be of a preferred shape, according to theform of open mesh winding desired. In the present instance, cam 24 isshown as a heartshaped cam which produces a linear traverse Imotion withminimum reversal angle. Cain 24 is driven through gears 28 which aredriven in synchronism with gears 30. As is shown, gears 30 drive thewinding arbor 32. As will be understood gears 28 and 30 are driven fromany desired source of power (not shown). The pusher arm 26 will traversethe width of the winding arbor 32 for each rotation of cam 24. The ratiobetween gears 28 and gears 30 will determine the number of times thatpusher arm 26 traverses winding arbor 32 for each rotation of thewinding arbor 32. This ratio will determine the amount of open areawithin the coil 10.

Winding machine 22 is provided with a iixed frame 34 to which isrotatably and movably attached the various components of winding machine22. Winding frame 34 includes a cross-arm 36, and a pivot arm 38 isprovided at one end to the cross arm 36 as shown at 40. The pivot arm 38is connected at its opposite end to pusher arm 26 as indicated at 42.Pusher arm 26 is spring mounted in mounting means 44 which is fixed tothe frame 34. The spring mounting `44 continuously forces pusher arm 26against cam 34 while allowing the arm 26 to move across the width ofwinding arbor 32 when pushed by cam 24. Of course, it will be understoodthat pusher arm 26 and mounting means 44 could be replaced by othertypes of cam followers, if desired.

The pivot arm 38 shown partially in phantom view, carries a wire feeddevice 46 which includes a pulley 48, a hollowing guiding finger 50 anda thin-walled, flexible, hollow needle 52. Wire 12 is fed from a feedroller (not shown) over pulley 48 through hollow guide 50 and hollowneedle 52 to the winding arbor 32. The stroke of pusher arm 26 is setfor a traverse slightly greater than the Width of arbor 32. Flanges 54are provided on the winding arbor 32. Thus when needle 52 is moved bypivot arm 38 and pusher arm 26 to the end of the traverse stroke, theneedle 52 will contact one of the flanges 54. With the over travel ofarms 26 and 38 the needle 52 flexes against the flange 54, holding wire12 against flange 54 for a short distance. This allows wire 12 toposition itself firmly against flange 54 so that it will not be pulledaway from flange 54 when the wire feed mechanism 46 reverses to traverseback across the winding arbor 32. As will be apparent, by the windingmethod herein described, a flexible needle 52 is provided moving with atraverse stroke slightly greater than the width of winding arbor 32.This provides a dwell of the wire 12 against the flange 54 sufficient toallow wire 12 to be firmly positioned against the yflange 54 before thereversal forces of 'the traverse mechanism are applied to the wire 12.The flanges 54 keep the turns of coil 10` in proper position during thewinding preventing wire falling oif during the winding operation. Aswill be apparent from FIGURE 2 of the drawing, pivot 40 is positionedalong cross arm 36 such that wire guide 50 and needle 52 will swingequal arcs about its center position between llanges 54.

In order to wind relatively thick coils, two or more inches thick, it isnecessary that the point of needle 52 should be substantially tangent tothe diameter of the coil 10. FIGURE 3 shows, in diagrammatic andschematic form, a side view of one means of mounting needle 52 on pivotarm 38 to insure that the needle S2 will remain tangent to the diameterof coil 410 as it is wound on arbor 32. As shown in FIGURE 3, arm 38 ispivoted at 40 on cross arm 36. Pulley 48, over which wire 12 is fed, issuspended below arm 38 by pulley support 56 which may be, for example, aU-shaped bracket depending from arm 38. A support arm 58 s provided, towhich is connected, at one end, wire guide 50 and needle 52. Theopposite end of support arm S8 is pivotally mounted on depending member60, as at 62. As shown, member 50 is mounted on arm .38 and extendsbelow arm 38 to substantially the center line 64 of winding arbor 32. Ofcourse, it will be understood that pivot point 62 is such that supportarm 58 is pivotal only in a vertical direction. Obviously, member .60and arm 58 must traverse the arbor 32, in the manner indicated in FIGURE2, to provide the desired crosswound coil 10. FIGURE 3 shows in phantomlines the plurality of positions taken by support arm 58, wire guide S0and needle 52 as the thickness of the winding increases on arbor 32.

Of course it will be understood that in using the winding machine 22either the epoxy glass mesh insulation, such as 16 and 18, or anovercoat, or both such means, may be used to stabilize the finishedcoil. After the winding 10 is completed on arbor 32 the winding isheated to cure either the epoxy insulation or the overcoat or both todirnensionally and physically stabilize the coil 10.

From the above it will be apparent that by means of this invention across Wound open mesh coil is provided which may be readily encapsulatedin any desired encapsulating resin. The open mesh of `the coil willreadily allow the encapsulating resin to completely fill all the voidsin the winding structure.

While there has been shown and described the present preferredembodiments of this invention, it will be understood that suchdescriptions are for illustrative purposes only. Obviously, many changesmay be made in the various constructional details without departing fromthe spirit or scope of the invention, particularly as it is dened in theappended claims.

What is claimed as new and which it is desired to secure by LettersPatent of the United States is:

I claim:

1. A cross-wound, open mesh coil comprising a plurality of turns of Wirecross wound to form an open mesh coil having at least 50% open areawithin such coil and having a layer of epoxy glass mesh insulationfirmly bonded to the inner and outer surfaces of said coil.

2. A cross-Wound, open mesh coil as claimed in claim 1 in which a resinovercoat material on said wire Iirmly bonds the cross-over points withinsaid coil, leaving said open area within said coil free of said resinmaterial.

3. A cross-wound, open mesh coil comprising a plurality of turns ofinsulated wire cross-Wound to form an open mesh coil having at least a50% open area Within said coil, the cross-over points within said coilbeing firmly bonded by a cured resin overcoat material on said insulatedwire leaving said open area free of said resin material.

References Cited UNITED STATES PATENTS 873,780 12/1907 Peterson 336-190XR 1,398,372 11/1921 Gowen 336-190 XR 2,195,233 3/1940 Boyer 336-206 XR2,282,759 5/ 1942 Gavitt 336-205 XR 2,295,958 9/ 1942 Lutz 336-206 XR2,489,867 ll/l949 DOrio 336-205 XR 2,780,742 2/ 1957 Iennen et al.336-205 XR 3,038,831 6/1962 Rosenberg 174-120 XR 3,237,136 2/1966 Ford336-205 20 LARAMIE E. ASKIN, Primary Examiner.

T. J. KOZMA, Assistant Examiner.

